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<p>Template declarations (both <a href="class_template.html" title="cpp/language/class template">class</a> and <a href="function_template.html" title="cpp/language/function template">function</a>) can appear inside a <a href="class.html" title="cpp/language/class">member specification</a> of any class, stuct, or union that aren't <a href="class.html%23Local_classes" title="cpp/language/class">local class</a>
</p>
<div class="t-example">
<div class="t-example-live-link"><div class="coliru-btn coliru-btn-run-init">Run this code</div></div>
<div dir="ltr" class="mw-geshi" style="text-align: left;"><div class="cpp source-cpp"><pre class="de1"><span class="co2">#include &lt;iostream&gt;</span>
<span class="co2">#include &lt;vector&gt;</span>
<span class="co2">#include &lt;algorithm&gt;</span>
 
<span class="kw1">struct</span> Printer <span class="br0">{</span> <span class="co1">// generic functor</span>
    <a href="../io/basic_ostream.html"><span class="kw1414">std::<span class="me2">ostream</span></span></a><span class="sy3">&amp;</span> os<span class="sy4">;</span>
    Printer<span class="br0">(</span><a href="../io/basic_ostream.html"><span class="kw1414">std::<span class="me2">ostream</span></span></a><span class="sy3">&amp;</span> os<span class="br0">)</span> <span class="sy4">:</span> os<span class="br0">(</span>os<span class="br0">)</span> <span class="br0">{</span><span class="br0">}</span>
    <span class="kw1">template</span><span class="sy1">&lt;</span><span class="kw1">typename</span> T<span class="sy1">&gt;</span>
    <span class="kw4">void</span> operator<span class="br0">(</span><span class="br0">)</span><span class="br0">(</span><span class="kw4">const</span> T<span class="sy3">&amp;</span> obj<span class="br0">)</span> <span class="br0">{</span> os <span class="sy1">&lt;&lt;</span> obj <span class="sy1">&lt;&lt;</span> <span class="st0">' '</span><span class="sy4">;</span> <span class="br0">]</span> <span class="co1">// member template</span>
<span class="br0">}</span><span class="sy4">;</span>
 
<span class="kw4">int</span> main<span class="br0">(</span><span class="br0">)</span>
<span class="br0">{</span>
    <a href="../container/vector.html"><span class="kw1067">std::<span class="me2">vector</span></span></a><span class="sy1">&lt;</span><span class="kw4">int</span><span class="sy1">&gt;</span> v <span class="sy1">=</span> <span class="br0">{</span><span class="nu0">1</span>,<span class="nu0">2</span>,<span class="nu0">3</span><span class="br0">}</span><span class="sy4">;</span>
    <a href="../algorithm/for_each.html"><span class="kw1263">std::<span class="me2">for_each</span></span></a><span class="br0">(</span>v.<span class="me1">begin</span><span class="br0">(</span><span class="br0">)</span>, v.<span class="me1">end</span><span class="br0">(</span><span class="br0">)</span>, Printer<span class="br0">(</span><a href="../io/basic_ostream.html"><span class="kw1439">std::<span class="me2">cout</span></span></a><span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
    <a href="../string/basic_string.html"><span class="kw1045">std::<span class="me2">string</span></span></a> s <span class="sy1">=</span> <span class="st0">"abc"</span><span class="sy4">;</span>
    <a href="../algorithm/for_each.html"><span class="kw1263">std::<span class="me2">for_each</span></span></a><span class="br0">(</span>s.<span class="me1">begin</span><span class="br0">(</span><span class="br0">)</span>, s.<span class="me1">end</span><span class="br0">(</span><span class="br0">)</span>, Printer<span class="br0">(</span><a href="../io/basic_ostream.html"><span class="kw1439">std::<span class="me2">cout</span></span></a><span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
<span class="br0">}</span></pre></div></div>
<p>Output:
</p>
<div dir="ltr" class="mw-geshi" style="text-align: left;"><div class="text source-text"><pre class="de1">1 2 3 a b c</pre></div></div> 
</div>
<p>If the enclosing class declaration is, in turn, a template itself, when member template is defined out of body, it takes two sets of template parameters: one for the enclosing class, and another for itself:
</p>
<div dir="ltr" class="mw-geshi" style="text-align: left;"><div class="cpp source-cpp"><pre class="de1"><span class="kw1">template</span><span class="sy1">&lt;</span><span class="kw1">typename</span> T<span class="sy1">&gt;</span>
<span class="kw1">struct</span> string <span class="br0">{</span>
    <span class="co1">// member template function</span>
    <span class="kw1">template</span><span class="sy1">&lt;</span><span class="kw1">typename</span> T2<span class="sy1">&gt;</span>
    <span class="kw4">int</span> compare<span class="br0">(</span><span class="kw4">const</span> T2<span class="sy3">&amp;</span><span class="br0">)</span><span class="sy4">;</span>
    <span class="co1">// constructors can be templates too</span>
    <span class="kw1">template</span><span class="sy1">&lt;</span><span class="kw1">typename</span> T2<span class="sy1">&gt;</span>
    string<span class="br0">(</span><span class="kw4">const</span> <a href="../string/basic_string.html"><span class="kw1043">std::<span class="me2">basic_string</span></span></a><span class="sy1">&lt;</span>T2<span class="sy1">&gt;</span><span class="sy3">&amp;</span> s<span class="br0">)</span> <span class="br0">{</span> <span class="coMULTI">/*...*/</span> <span class="br0">}</span>
<span class="br0">}</span><span class="sy4">;</span>
<span class="co1">// out of class definition of string&lt;T1&gt;::compare&lt;T2&gt; </span>
<span class="kw1">template</span><span class="sy1">&lt;</span><span class="kw1">typename</span> T1<span class="sy1">&gt;</span> <span class="co1">// for the enclosing class template</span>
<span class="kw1">template</span><span class="sy1">&lt;</span><span class="kw1">typename</span> T2<span class="sy1">&gt;</span> <span class="co1">// for the member template</span>
<span class="kw4">int</span> string<span class="sy1">&lt;</span>T1<span class="sy1">&gt;</span><span class="sy4">::</span><span class="me2">compare</span><span class="br0">(</span><span class="kw4">const</span> T2<span class="sy3">&amp;</span> s<span class="br0">)</span> <span class="br0">{</span> <span class="coMULTI">/* ... */</span> <span class="br0">}</span></pre></div></div>
<h3>
<span class="editsection">[<a href="http%3A//en.cppreference.com/mwiki/index.php" title="Edit section: Member function templates">edit</a>]</span> <span class="mw-headline" id="Member_function_templates">Member function templates</span>
</h3>
<p>Destructor and copy constructor cannot be templates, but other special member functions can be. If a template constructor is declared which could be instantiated with the type signature of a <a href="copy_constructor.html" title="cpp/language/copy constructor">copy constructor</a>, the implicitly-declared copy constructor is used instead.
</p>
<p>A member function template cannot be virtual, and a member function template in a derived class cannot override a virtual member function from the base class.
</p>
<div dir="ltr" class="mw-geshi" style="text-align: left;"><div class="cpp source-cpp"><pre class="de1"><span class="kw1">class</span> Base <span class="br0">{</span>
    <span class="kw1">virtual</span> <span class="kw4">void</span> f<span class="br0">(</span><span class="kw4">int</span><span class="br0">)</span><span class="sy4">;</span>
<span class="br0">}</span><span class="sy4">;</span>
<span class="kw1">struct</span> Derived <span class="sy4">:</span> Base <span class="br0">{</span>
    <span class="co1">// this member template does not override B::f</span>
    <span class="kw1">template</span> <span class="sy1">&lt;</span><span class="kw1">class</span> T<span class="sy1">&gt;</span> <span class="kw4">void</span> f<span class="br0">(</span>T<span class="br0">)</span><span class="sy4">;</span>
 
    <span class="co1">// non-member override can call the template:</span>
    <span class="kw4">void</span> f<span class="br0">(</span><span class="kw4">int</span> i<span class="br0">)</span> override <span class="br0">{</span>
         f<span class="sy1">&lt;&gt;</span><span class="br0">(</span>i<span class="br0">)</span><span class="sy4">;</span>
    <span class="br0">}</span>
<span class="br0">}</span><span class="sy4">;</span></pre></div></div>
<p>A non-template member function and a template member function with the same name may be declared. In case of conflict (when some template specialization matches the non-template function signature exactly), use of that name and type refers to the non-template member unless an explicit template argument list is supplied.
</p>
<div dir="ltr" class="mw-geshi" style="text-align: left;"><div class="cpp source-cpp"><pre class="de1"><span class="kw1">template</span><span class="sy1">&lt;</span><span class="kw1">typename</span> T<span class="sy1">&gt;</span>
<span class="kw1">struct</span> A <span class="br0">{</span>
    <span class="kw4">void</span> f<span class="br0">(</span><span class="kw4">int</span><span class="br0">)</span><span class="sy4">;</span> <span class="co1">// non-template member</span>
    <span class="kw1">template</span><span class="sy1">&lt;</span><span class="kw1">typename</span> T2<span class="sy1">&gt;</span> <span class="kw4">void</span> f<span class="br0">(</span>T2<span class="br0">)</span><span class="sy4">;</span> <span class="co1">// member template</span>
<span class="br0">}</span><span class="sy4">;</span>
 
<span class="kw4">int</span> main<span class="br0">(</span><span class="br0">)</span>
<span class="br0">{</span>
    A<span class="sy1">&lt;</span><span class="kw4">char</span><span class="sy1">&gt;</span> ac<span class="sy4">;</span>
    ac.<span class="me1">f</span><span class="br0">(</span><span class="st0">'c'</span><span class="br0">)</span><span class="sy4">;</span> <span class="co1">// calls template function A&lt;char&gt;::f&lt;char&gt;(int)</span>
    ac.<span class="me1">f</span><span class="br0">(</span><span class="nu0">1</span><span class="br0">)</span><span class="sy4">;</span>   <span class="co1">// calls non-template function A&lt;char&gt;::f(int)</span>
    ac.<span class="me1">f</span><span class="sy1">&lt;&gt;</span><span class="br0">(</span><span class="nu0">1</span><span class="br0">)</span><span class="sy4">;</span> <span class="co1">// calls template function A&lt;char&gt;::f&lt;int&gt;(inf)</span>
<span class="br0">}</span></pre></div></div>
<h3>
<span class="editsection">[<a href="http%3A//en.cppreference.com/mwiki/index.php" title="Edit section: Conversion function templates">edit</a>]</span> <span class="mw-headline" id="Conversion_function_templates">Conversion function templates</span>
</h3>
<p>A user-defined <a href="cast_operator.html" title="cpp/language/cast operator">conversion function</a> can be a template.
</p>
<div dir="ltr" class="mw-geshi" style="text-align: left;"><div class="cpp source-cpp"><pre class="de1"><span class="kw1">struct</span> A <span class="br0">{</span>
    <span class="kw1">template</span><span class="sy1">&lt;</span><span class="kw1">typename</span> T<span class="sy1">&gt;</span>
    operator T<span class="sy2">*</span><span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span> <span class="co1">// conversion to pointer to any type</span>
<span class="br0">}</span><span class="sy4">;</span>
 
<span class="co1">// out-of-class definition</span>
<span class="kw1">template</span><span class="sy1">&lt;</span><span class="kw1">typename</span> T<span class="sy1">&gt;</span>
A<span class="sy4">::</span><span class="me2">operator</span> T<span class="sy2">*</span><span class="br0">(</span><span class="br0">)</span> <span class="br0">{</span><span class="kw1">return</span> nullptr<span class="sy4">;</span><span class="br0">}</span>
 
<span class="co1">// explicit specialization for char*</span>
<span class="kw1">template</span><span class="sy1">&lt;&gt;</span>
A<span class="sy4">::</span><span class="me2">operator</span> <span class="kw4">char</span><span class="sy2">*</span><span class="br0">(</span><span class="br0">)</span> <span class="br0">{</span><span class="kw1">return</span> nullptr<span class="sy4">;</span><span class="br0">}</span>
 
<span class="co1">// explicit instantiation</span>
<span class="kw1">template</span> A<span class="sy4">::</span><span class="me2">operator</span> <span class="kw4">void</span><span class="sy2">*</span><span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span>
 
<span class="kw4">int</span> main<span class="br0">(</span><span class="br0">)</span> <span class="br0">{</span>
    A a<span class="sy4">;</span>
    <span class="kw4">int</span><span class="sy2">*</span> ip <span class="sy1">=</span> a.<span class="me1">operator</span> <span class="kw4">int</span><span class="sy2">*</span><span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span> <span class="co1">// explicit call to A::operator int*()</span>
<span class="br0">}</span></pre></div></div>
<p>During <a href="overload_resolution.html" title="cpp/language/overload resolution">overload resolution</a>, specialization of conversion function templates are not found by <a href="lookup.html" title="cpp/language/lookup">name lookup</a>. Instead, all visible conversion function templates are considered, and every specialization produced by <a href="template_argument_deduction.html" title="cpp/language/template argument deduction">template argument deduction</a> (which has special rules for conversion function templates) is used as if found by name lookup.
</p>
<p>Using-declarations in derived classes cannot refer to specializations of template conversion functions from base classes.
</p>
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